A hybrid electric vehicle powertrain includes an engine and an electric motor, wherein torque produced by the engine and/or by the motor can be transferred through a transmission to the vehicle drive wheels to propel the vehicle. A traction battery supplies energy to the motor for the motor to produce the positive motor torque for propelling the vehicle. The motor may provide negative motor torque to the transmission (for example, during regenerative braking of the vehicle) and thereby act as a generator to the battery. The engine may also provide negative engine torque to the transmission to provide engine braking for powertrain braking of the vehicle.
In a modular hybrid transmission (“MHT”) configuration, the engine is connectable to the motor by a disconnect clutch and the motor is connected to the transmission. The engine, the disconnect clutch, the motor, and the transmission are connected sequentially in series.
The hybrid electric vehicle may also include a four-wheel or all-wheel drive (AWD) driveline, to provide better traction than a two-wheel drive vehicle. To improve fuel economy in an AWD vehicle, the vehicle may normally operate in a two-wheel drive mode and selectively engage all four wheels only when conditions necessitate greater traction.